This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Method for Controlling Paper Feed of a Liquid Electrophotographic Color Printer earlier filed in the Korean Industrial Property Office on Nov. 20, 1999, and there duly assigned Ser. No. 99-51741 by that Office.
1. Field of the Invention
The present invention relates to a method for controlling paper feeding of a liquid electrophotographic color printing device, and more particularly, to a method for controlling the paper feeding of a liquid electrophotographic color printing device capable of minimizing the occurrence of a paper jam by variably adjusting the speed of the paper feeding roller in accordance with the delay period when the paper feeding is delayed at a paper feeding path.
2. Description of the Background Art
In general, a liquid electrophotographic color printing device prints an image by forming an electrostatic latent image on a photosensitive medium such as a photosensitive belt by projecting a laser beam, developing the electrostatic latent image by using a developer in which a solid toner having a certain color is mixed with a carrier serving as solution for the toner, and transferring the image onto a paper. The image is transferred onto the paper around a transfer unit.
The electrostatic printer will have multiple sensors located around the paper feeding path. The sensors allow the printer to monitor if there is any delay in the paper moving along the paper path. If there is a delay at any point, the printer stops the movement of the paper along the paper path until the problem is corrected.
In case of a paper feeding delay, by detecting such a feeding delay of the paper and by accordingly stopping the paper feeding, the print quality deterioration caused due to the feeding delay is prevented.
The paper feed controlling method of the conventional liquid electrophotographic color printing device as described above, however, simply stops the feeding operation while simultaneously displaying the jamming error whenever detecting the paper feed delay on the paper feed path, and accordingly has a drawback of frequent stoppage of printing operation when the jamming frequently occurs. More specifically, in the liquid electrophotographic color printing device, the printing operation is frequently stopped by the jamming errors, when the paper feed delay occurs due to other reasons such as the slipping of the rollers, the operation delay of the clutches, the mis-picking of the paper, or the troubles on the paper feed path.
Moreover, in the conventional liquid electrophotographic color printing device having a long paper feed path, during a continuous printing of letter papers on the paper feed path, multiple sheets of letter paper should be simultaneously fed on the paper feed path at uniform intervals and also with stable paper curl at the last paper feeding roller closest to the transfer unit in order to prevent printing quality deterioration. However, in the conventional printing device, it is hard to keep sheets of letter paper at uniform intervals since paper feed delays frequently occur due to the above reasons. Moreover, the unstable occurrence of the paper curl at the last paper feeding roller also deteriorates print quality.
Exemplars of the background art, U.S. Pat. No. 5,713,059 for Paper Jam Detector for Electrophotographic Printer issued to Ishikawa, U.S. Pat. No. 5,534,976 for Method for Eliminating a Paper of an Image Forming System and Apparatus Therefor issued to Kim, U.S. Pat. No. 5,580,046 for Selective Ejection of Sensed Paper Jams in Single Sheet Paper Processing Equipment issued to Beaufort et al., U.S. Pat. No. 5,822,668 for Fuser Subsystem Module for an Electrophotographic Printer Which Pivots Open for Jam Clearance issued to Fromm et al., U.S. Pat. No. 3,948,510 for Sheet Jam Detector for Electrophotographic Copying Machine issued to Iwamoto et al., U.S. Pat. No. 5,365,322 for Image Forming Apparatus Which Detects a Jam of a Wound Sheet issued to Hamada et al., U.S. Pat. No. 5,963,754 for Medium Detection Unit, Medium Conveyance Apparatus and Image Formation System Including a Single Sensor Which Detects Medium Passage, a Fully Accumulated Condition and a Jam Condition issued to Itoh et al. disclose paper jam detectors for electrophotographic printing devices. I have found that the art does not show a way to minimize the occurrence of paper jams.
The present invention has been developed to overcome the above mentioned problems of the art, and accordingly it is an object of the present invention to provide a paper feed controlling method of a liquid electrophotographic color printing device for minimizing the occurrence of a paper jam by compensating a paper feed delay when the delay occurs on a paper feeding path, for controlling steady occurrence of paper curl during a continuous printing of multiple letter papers, and for maintaining letter papers at uniform intervals.
It is another object to have a paper jam monitor that can avoid multiple stoppages of the transfer of paper through an electrophotographic printer.
It is a further object to have an electrophotographic printer that can rapidly print on paper while minimizing paper jams.
It is yet another object to have a method of adjusting the transfer rate of the paper through a paper path according to any delay of the paper transporting through the paper path.
It is yet a further object to have a printer that can effectively minimize the occurrence of paper jams in a printer that has a long paper path and handles multiple types of papers.
Accordingly, to achieve the above object, the present invention provides a paper feed control method of a printing device including picking up a sheet of paper accommodated in a paper cassette and forwarding the paper to a paper feeding path formed between the paper cassette and a transfer/securing unit of the printing device; feeding the paper forwarded to the paper feeding path; detecting the feed speed of the paper being fed along the paper feeding path; determining whether the paper is delayed or not in accordance with the result of the step of detecting the feed speed; and compensating the feed speed of the paper by increasing the feed speed when the paper is determined to be delayed.
The above object is also accomplished by a paper feed control method of a paper feeding device of a liquid electrophotographic color printing device having a multiple paper cassettes for accommodating various sizes and types of paper; a pickup roller assembly for picking a sheet of the paper from the paper cassettes and forwarding the paper to a paper feeding path; a first, a second, a third, a fourth, and a fifth paper feeding rollers arranged in pairs at certain intervals on the paper feeding path, for feeding the paper; first and second driving motors for driving the first, second, third, fourth, and fifth paper feeding rollers and the pickup roller assembly; multiple first clutches for selectively connecting the first driving motor with the pickup roller assembly, the first paper feeding roller, or the second paper feeding roller; multiple second clutches for selectively connecting the second driving motor with the third paper feeding roller, the fourth paper feeding roller, or the fifth paper feeding roller; and first, second, third, fourth, and fifth jamming detecting sensors, installed adjacent to the first, second, third, fourth, and fifth paper feeding rollers, for detecting the paper passing there through. The paper feed control method first detects the feeding speed of the paper being passed through the respective paper feeding rollers by the first through the fifth jamming detecting sensors. This step measures the time right after the driving of the first paper feeding roller until the paper arrives at the third jamming detecting sensor. Secondly, the presence of a paper delay is determined in accordance with the detected result in the step of detecting the feeding speed. The second step determines the paper feed delay when the paper arrival time at a certain part is later than the preset paper feeding time for the certain part by comparing the paper arrival time at the certain part detected by the third jamming detecting sensor with the preset paper feeding time for the certain part. Thirdly, the paper feed delay is compensated by adjusting the rotational speed of the paper feeding rollers according to the determined paper feed delay. The final step adjusts the rotational speed of the second driving motor to vary the rotational speed of a paper feeding roller which is driven by the second driving motor.
The paper feed control method further includes an additional step of returning the adjusted rotational speed of the second driving motor to the initial rotational speed after driving the second driving motor at the adjusted rotational speed for a certain length of time. Here, the rotational speed of the second driving motor is returned to the initial rotational speed when the paper is detected by the fifth jamming detecting sensor.
According to the features of the present invention, since the rotational speed of the corresponding paper feeding roller is compensated to be varied based on the degree of the paper feed delay without stopping the paper feeding even when the paper feed delay is detected on the paper feeding path, the frequency of the paper jamming can be decreased. Accordingly, frequent interruptions of the printing job due to the jamming error are prevented. Further, since the occurrence of paper curl at the fifth paper feed roller is consistently controlled, and since the papers are kept at uniform intervals during continuous printing operation, the deterioration of the print quality can be prevented.